//给你一棵二叉树的根节点 root ，翻转这棵二叉树，并返回其根节点。 
//
// 
//
// 示例 1： 
//
// 
//
// 
//输入：root = [4,2,7,1,3,6,9]
//输出：[4,7,2,9,6,3,1]
// 
//
// 示例 2： 
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// 
//
// 
//输入：root = [2,1,3]
//输出：[2,3,1]
// 
//
// 示例 3： 
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// 
//输入：root = []
//输出：[]
// 
//
// 
//
// 提示： 
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// 
// 树中节点数目范围在 [0, 100] 内 
// -100 <= Node.val <= 100 
// 
// Related Topics 树 深度优先搜索 广度优先搜索 二叉树 👍 1212 👎 0

package leetcode.editor.cn;

import java.util.ArrayDeque;
import java.util.Queue;

public class _226_InvertBinaryTree {

    public static class TreeNode {
        int val;
        TreeNode left;
        TreeNode right;

        TreeNode() {
        }

        TreeNode(int val) {
            this.val = val;
        }

        TreeNode(int val, TreeNode left, TreeNode right) {
            this.val = val;
            this.left = left;
            this.right = right;
        }
    }

    public static void main(String[] args) {
        Solution solution = new _226_InvertBinaryTree().new Solution();
        TreeNode root = new TreeNode(4,
                new TreeNode(2, new TreeNode(1), new TreeNode(3)),
                new TreeNode(7, new TreeNode(6), new TreeNode(9)));
        solution.invertTree(root);
        bfs(root);
    }

    private static void bfs(TreeNode root) {
        if (root == null) return;

        Queue<TreeNode> queue = new ArrayDeque<>();
        queue.add(root);
        while (!queue.isEmpty()) {
            TreeNode tmp = queue.poll();
            if (tmp.left != null) queue.add(tmp.left);
            if (tmp.right != null) queue.add(tmp.right);

            System.out.print(tmp.val + " ");
        }
    }
    //leetcode submit region begin(Prohibit modification and deletion)

    /**
     * Definition for a binary tree node.
     * public class TreeNode {
     * int val;
     * TreeNode left;
     * TreeNode right;
     * TreeNode() {}
     * TreeNode(int val) { this.val = val; }
     * TreeNode(int val, TreeNode left, TreeNode right) {
     * this.val = val;
     * this.left = left;
     * this.right = right;
     * }
     * }
     */
    class Solution {
        public TreeNode invertTree(TreeNode root) {
            if (root == null) return root;
            invertTree(root.left);
            invertTree(root.right);

            TreeNode tmp = root.left;
            root.left = root.right;
            root.right = tmp;

            return root;
        }
    }
//leetcode submit region end(Prohibit modification and deletion)

}